Illumination refers to the technique of using all kinds of light sources to illuminate certain environments and locations. The development of illumination extends the work and rest time of modem people. The illuminating light in the darkness broadens the human horizon and also breaks the barrier between day and night. The utilization of illumination has to be based on the users' standpoint, namely, the use of illumination is user-oriented. Under this premise, eyesight protection is taken as a top priority when using light, because health is the foundation of all human accomplishments. The second priority is the quality of illumination, that is to say, to provide a good environment of illumination. The last priority is to conserve energy, increasing luminaire efficiency and saving a considerable sum of electricity consumption.
To achieve the goal of eyesight protection, “illuminance” is a top issue. Illuminance refers to “the brightness of an illuminated object”. In order to provide an environment for eyes to comfortably recognize an object, provision of enough illuminance is necessary. In addition to providing appropriate illuminance, the light should also be distributed evenly to avoid a strong light contrast which leads to tired eyes.
For the time being, although there is a minor number of illumination devices equipped with a brightness adjusting function, the output illuminance is often insufficient or excessive, causing negative effects on eye health. The reasons are that the users do not know the exact illuminance value and can only adjust the brightness out of instinct, and that the conventional illumination system cannot adjust the illuminance precisely according to the users' adjustment.